The reflow soldering apparatus solders, for example, a printed circuit board on which electronic components have been mounted using cream solder, solder paste, or the like while conveying the board on a conveyor, inside a furnace having a preheating process, a reflow process, and a cooling process in sequence (See Patent Document 1).
Patent Document 2 discloses a method for conveying a board in a reflow furnace. A conveyor system disclosed in Patent Document 2 includes a main endless conveyor belt configured to extend from an inlet to an outlet of a reflow furnace and operated at a constant speed. A board conveyance path is formed to convey boards from the inlet to the outlet of the reflow furnace on the main endless conveyor belt. On the board conveyance path, plural pushers are placed, being spaced away from each other in a workpiece conveyance direction, and each of the pushers reciprocates in directions the same as and opposite to the workpiece conveyance direction. The pusher can push the board on the main endless conveyor belt upward and convey the board in the workpiece conveyance direction at a controlled speed. An endless belt has been adopted to reciprocate the pushers attached to the endless belt. When the endless belt rotates in a forward direction, the pusher moves in the workpiece conveyance direction, and when the endless belt rotates in a reverse direction, the pusher moves in the direction opposite to the workpiece conveyance direction.
A first pusher included in the plural pushers is used to send a board into a reflow process of the reflow furnace. A second pusher is used to send the board out of the reflow process and convey the board from the reflow process to a cooling process. The first and second pushers are controlled to move independently of the main endless conveyor belt at a speed faster than that of the main endless conveyor belt.
In soldering using a reflow furnace, preferably a degassing process is applied in advance to avoid foaming in accompanying with heating. For example, in the reflow soldering apparatus shown in Patent Document 1, when a decompression chamber capable of reducing ambient pressure is installed on a board conveyance path such that a soldered portion formed on the board and molten by heating will be degassed in the decompression chamber, a single conveyor (main endless conveyor belt) cannot be installed over the entire board conveyance path including the decompression chamber because the decompression chamber needs to be enclosed hermetically during decompression. Therefore, separate conveyors are installed in the decompression chamber and in conveyance paths in processes preceding and succeeding the decompression chamber. In this case, if a conveyor is installed in the decompression chamber, there is a problem in that mechanical components of the conveyor become expensive to withstand a decompressed atmosphere and that maintenance frequency is increased.
With the board conveyance method described in Patent Document 2, air cylinders are used to move the pushers up and down, resulting in increased maintenance frequency. Also, the air cylinders themselves need to be moved in the conveyance direction.
Patent Document 1
Japanese Patent Laid-Open No. 2000-188467
Patent Document 2
Japanese Patent Laid-Open No. 11-40941